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DIY Stompboxes => Building your own stompbox => Topic started by: Zounds! on December 06, 2017, 11:15:23 PM

Title: Mu-Tron Phasor II (clone) debug
Post by: Zounds! on December 06, 2017, 11:15:23 PM
My Mu-Tron Phasor II build is only passing clean, unaffected signal. No phasing sound, though there is a tick that can be sped up or slowed down by adjusting the rate pot. Also, my LED is not lighting at all. Schematic and parts list here: http://www.pedalpcb.com/docs/PhaseII.pdf

Substitutions: I used a MAX1044 instead of TC1044. R35 is socketed, but I have the stock value in there now. I had to rig up resistors in series to get the right values for R1, R3, and R29.

I've done some searching but can't figure out what voltages I should be seeing. I figure mine are very off, but hopefully the repeating voltage patterns throughout suggest that a single error is causing the issue throughout?:


Power Supply
9.15v

IC1
0.0      8.84
0.0      0.0
0.0      0.0
-8.14   0.0

IC2
-6.15    -6.89
-3.06    -6.31
0.0       -6.23
-8.14     0.0

IC3
0.0      8.84
0.0      0.0
0.0      0.0
-8.14   0.0

IC4
0.0       8.84
0.0       0.0
0.0       0.0
-8.14    0.0

IC5
3.48      8.84
0.0        0.0
0.7        0.0
-8.14     0.0

IC6
0.0       8.16
0.0      -0.31
-0.18    0.0
-8.14    0.0

IC7
8.84    8.84
4.36    6.59
0.0      4.21
-4.13   -8.15

Q1
E: 5.62
B: 3.48
C: 8.84

LED (long leg through the square pad on the PCB...but now that Iím typing out these measurements, maybe I put it in backwards?)
+: 0.0
-: 5.62

And some pics. Sorry about the huge 470nf caps getting in the way. They're all I had!

(http://img.photobucket.com/albums/v401/vivalaben1/IMG_3983.jpg)
(http://img.photobucket.com/albums/v401/vivalaben1/IMG_3984.jpg)
(http://img.photobucket.com/albums/v401/vivalaben1/IMG_3985.jpg)
(http://img.photobucket.com/albums/v401/vivalaben1/IMG_3986.jpg)

Thanks in advance for any advice on troubleshooting this one!
Title: Re: Mu-Tron Phasor II (clone) debug
Post by: Slowpoke101 on December 07, 2017, 12:18:54 AM
Looking at the component overlay from the build documentation, and I may be wrong.
Remove the yellow LED and reinstall 180 degrees from its current rotation. The flat on the LED body goes towards the top of the board.
Try it again and see what happens.
Title: Re: Mu-Tron Phasor II (clone) debug
Post by: bluebunny on December 07, 2017, 02:44:11 AM
[ PLEASE UPDATE YOUR ACCOUNT TO ENABLE 3RD PARTY HOSTING ]

 :(
Title: Re: Mu-Tron Phasor II (clone) debug
Post by: Zounds! on December 07, 2017, 08:46:02 PM
Ah, the LED was backwards! It's on now and flickers in time with the rate pot, but still no phasing sound. Here are my new voltages:

IC1
0.0       8.84
0.0       0.0
0.0       0.0
-8.14    0.0

IC2
-6.15    -6.89
-3.06    -6.31
0.0       -6.23
-8.14     0.0

IC3
0.0      8.84
0.0      0.0
0.0      0.0
-8.14   0.0

IC4
0.0       8.84
0.0       0.0
0.0       0.0
-8.14    0.0

IC5
0.0       8.84
0.1       0.0
0.07     0.0
-8.14    0.0

IC6
~1v (swinging up and down rapidly)       8.16
0.0                                                       1v (swinging up and down rapidly)
~1v (swinging up and down rapidly)       0.0
-8.14                                                    0.0

IC7
8.84    8.84
4.36    6.59
0.0      4.21
-4.13   -8.15

Q1
E: ~2v (swinging up and down rapidly)
B: ~1v (swinging up and down rapidly)

C: 8.84

LED
+: 1.81
-: 0.5

Power Supply
9.15v

And let's try this again with the photos:

(https://s2.postimg.org/nv4wqs6bp/IMG_3983.jpg) (https://postimg.org/image/nv4wqs6bp/)

(https://s2.postimg.org/fe5efb41h/IMG_3984.jpg) (https://postimg.org/image/fe5efb41h/)

(https://s2.postimg.org/siays0qyd/IMG_3985.jpg) (https://postimg.org/image/siays0qyd/)

(https://s2.postimg.org/mu4o14ubp/IMG_3986.jpg) (https://postimg.org/image/mu4o14ubp/)
Title: Re: Mu-Tron Phasor II (clone) debug
Post by: thermionix on December 07, 2017, 09:31:26 PM
Have you tried it in the dark?
Title: Re: Mu-Tron Phasor II (clone) debug
Post by: Zounds! on December 07, 2017, 09:43:03 PM
Yup, I did try it in the dark too. No difference.
Title: Re: Mu-Tron Phasor II (clone) debug
Post by: Slowpoke101 on December 07, 2017, 11:12:20 PM
IC2 voltages look really odd. Pin 8 should be about positive 8 Volts and not a negative voltage. You may have a break in the track feeding power to pin 8 so check this out.
Make sure that when you test this unit for phasing action that it is placed in the dark. Any level of ambient light causes the LDRs not to work correctly.
Good luck.
Title: Re: Mu-Tron Phasor II (clone) debug
Post by: duck_arse on December 08, 2017, 09:38:15 AM
(https://s2.postimg.org/mu4o14ubp/IMG_3986.jpg)

in this image, just about where IC2 is, there is a quartet of copper coloured marks where all else around is black. is there a chance that is a pair of open/damaged tracks? there is a couple of similar marks lower centre of the board, might as well check those too.
Title: Re: Mu-Tron Phasor II (clone) debug
Post by: Zounds! on December 08, 2017, 11:12:15 PM
Pin 8 of IC2 was the problem! It wasn't making a connection with the trace that feeds power to IC2, IC3, and IC4. The trace that connects them is on the top of the board and covered with components, so rather than disassemble I just added a jumper between pin 8 of IC2 and pin 8 of IC3. No more funky negative voltages on IC2 and the effect sounds awesome! Thanks as usual for you folks' help!